This disclosure relates generally to electrostatographic reproduction systems, and more specifically, it is directed to a common polarity toner image duplexing electrostatographic reproduction machine.
The basic process of monocolor electrostatographic reproduction (e.g. black image placed on a white background) comprises exposing a charged photoconductive member. The irradiated areas of the photoconductive surface are discharged to record thereon an electrostatic latent image corresponding to the original document.
In electrostatographic reproduction includes cases where an electrostatic charge is deposited image-wise on a dielectric photoconductive member as well as electrophotographic reproduction in which an overall electrostatically charged photoconductive dielectric photoconductive member is image-wise exposed to conductivity increasing radiation producing thereby a xe2x80x9cdirectxe2x80x9d or xe2x80x9creversalxe2x80x9d toner-developable charge pattern on the photoconductive member. xe2x80x9cDirectxe2x80x9d development involves positive-positive development between charge and toner, and is particularly useful for reproducing pictures and text. xe2x80x9cReversalxe2x80x9d development is of interest when from a negative original a positive reproduction has to be made or vice-versa, or when the exposure derives from an image in digital electrical signal form, wherein the electrical signals modulate a laser beam or the light output of light-emitting diodes (LEDs). It is advantageous with respect to a reduced load of the electric signal modulated light source (laser or LEDs) to record graphic information (e.g. printed text) in such a way that the light information corresponds with the graphic characters so that by xe2x80x9creversalxe2x80x9d development in the exposed area of a photoconductive recording layer, toner can be deposited to produce a positive reproduction of an electronic original.
A development system, thereupon, moves a developer mix of carrier granules and toner particles into contact with the photoconductive surface. The toner particles are attracted electrostatically from the carrier granules to the latent image forming a toner powder image thereon. Thereafter, the toner powder image is transferred to a sheet of support material. Following the toner image transfer to the sheet of support material, the support material sheet advances to a fuser which permanently affixes the toner powder image thereto.
Essentially, multicolor electrostatographic copying and reproduction (e.g. several colors placed on a white background) repeats the process of monocolor reproduction by repeating a plurality of cycles, each cycle being for a different color. Development stations for each of the different colors apply a specific color toner complimentary in color to the color of a filter utilized to produce the irradiated areas of the photoconductive member. The different color toners are generally, cyan, magenta, and yellow (and sometimes black if a true black is desired), which in one combination or another can be used to generate the full spectrum of visible colors.
Through the application of the different colored toners at the respective stations, a plurality of color toner powder images are formed for transfer directly to a sheet of support material or to an intermediate belt for subsequent transfer to a sheet of support material. In either case the images are transferred in superimposed registration with one another. After a plurality of different color toner powder images have been transferred to the sheet of support material in superimposed registration with one another, the multicolor toner powder image is permanently affixed thereto.
In recent years, there have been demands for machines, for example duplex machines, providing high productivity, high quality images. Such a machine is disclosed for example in EP0629924 (assigned to Xeikon) and comprises an electrostatographic single-pass duplexing multiple station multi-color reproduction machine. In it a toner image is formed on a photoconductive member of an imaging modules and is then transferred to a paper receiving sheet such as a continuous web whereon the toner image is treated with a pair of opposed corona generating corotrons or xe2x80x9cduetsxe2x80x9d and is then fused. Thereafter, the web is usually then cut into sheets containing the desired image frames.
The opposed corona generating corotrons or xe2x80x9cduetxe2x80x9d arrangement in such a machine is disadvantageous in that it requires use of many corotrons. For example, two corotrons (one on top of the paper and another on the bottom of the paper opposing the top corotron) are needed as a duet for every imaging modules. In a seven imaging modules duplexing machine for example, this translates to 14 corotrons for the duet function.
Duets are used in the Xeikon configuration mainly to xe2x80x9ccorrectxe2x80x9d the toner charge prior to each color imaging module. In practice xe2x80x9ccorrectionxe2x80x9d means charging xe2x80x9cthe toner on the side of the paper that will face the next imaging module""s drumxe2x80x9d toward the same polarity that the toner has on the next imaging drum. The alternative would be a more expensive use of different polarity toners.
There is therefore a need for an economical common polarity toner duplexing electrostatographic reproduction machine.
In accordance with the present disclosure, there is provided a common polarity duplexing electrostatographic reproduction machine that includes (i) a first plurality of toner image producing electrostatographic modules that each include a first image forming surface, image forming devices, and charged toner particles having a first polarity, (ii) a second plurality of toner image producing electrostatographic modules that each have a second image forming surface, image forming devices, including charged toner particles having a polarity common with the first polarity, (iii) a charged toner polarity reversing device mounted against each module of the second plurality of toner image producing electrostatographic modules for reversing a polarity of toner particles forming the second set of toner images from the first polarity to a second an opposite polarity; and (iv) a transfer device for transferring the second set of toner images having the second polarity onto a second side of the web of recording media.